In particular, the present invention relates to a tire curing device of the type comprising a mold defining a toroidal chamber for accommodating a tire to be cured; a closed circuit for a batch charge of a heat exchange fluid, said chamber forming part of the closed circuit; powered circulating means assigned to the closed circuit for force circulating the heat exchange fluid along same; and heating means assigned to the closed circuit for heating the heat exchange fluid to a predetermined temperature. A prior art curing device of the above type is described in detail in U.S. Pat. No. 4,747,765, the content of which is fully incorporated herein by reference.
In the curing device described in the noted patent, a central curing unit is mounted through the mold; houses both the forced circulating and heating means; and is so designed as to define both a delivery and return conduit for the heat exchange fluid to and from the toroidal chamber.
This prior art curing device presents a number of functional drawbacks, mainly due to the design of the heating means and the return conduit to which the heating means are assigned. In the noted prior art curing device, the heating means consist of a heating element comprising a block of sintered material fitted inside the central unit, coaxial with the mold, and constituting, for the return conduit, a plug fitted through with a number of parallel, substantially axial channels along which the heat exchange fluid flows to the inlet of the circulating means.
Each channel houses an incandescent electrical resistor lapped directly by the heat exchange fluid, which is thus heated to the temperature required for curing a green tire housed inside the toroidal chamber. The swirl induced by the known heating element in the heat exchange fluid and immediately upstream from the circulating means is such as to seriously impair the efficiency of the circulating means and, therefore, the speed at which the heat exchange fluid enters the toroidal chamber.
Moreover, the known heating element is extremely delicate from the functional standpoint. Even the slightest interruption, caused by any external phenomena, in the flow of heat exchange fluid along the channels, invariably results in immediate melting of at least part of the electrical resistors inside the channels, so that the entire heating element must be replaced. This involves dismantling and opening up the central unit, thus resulting in considerable downtime.